Hmm... what does "text-based front end" mean, and is there another kind? Is the standard notebook interface a text-based front end? What's an example of a non-text-based front end for Mathematica?
Trace suggests !expr is interpreted the same as Not[expr] for SOME expressions, at least:
!PrimeQ[12]//Trace
{{PrimeQ[12],False},!False,True}
But, indeed, if I input:
!True
a DOS window comes up briefly and disappears before I can tell what's up. This is a huge surprise to me.
Type this to see the DOS window more clearly:
!pause
Or better yet,
!cmd
However, if I input
!PrimeQ[12]
there is no fleeting DOS window, and still no Output cell. Is that because cmd is a DOS command, but PrimeQ[12] isn't? Can Mathematica be certain of this? (True isn't a DOS command, after all.)
Does "escape sequence" mean "DOS command"? No, I guess not, since
!dir>dum.txt
doesn't pipe directory contents to a file called "dum.txt". (It doesn't do anything at all, as far as I can tell.) So... what's really going on, I wonder?
Bobby
On Sun, 10 Apr 2005 23:07:10 -0400 (EDT), David Park <djmp at earthlink.net> wrote:
> DongGook,
>
> Read the rest of the Help for Not, at least on Version 5...
>
> If you are using Mathematica with a text-based front end, then you cannot
> use the notation !expr for Not[expr] if it appears at the very beginning of
> a line. In this case, !expr is interpreted as a shell escape.
>
> (Certainly a strange 'feature'!)
>
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
>
> From: DongGook Park [mailto:dgpark6 at sunchon.ac.kr]
To: mathgroup at smc.vnet.net
> To: mathgroup at smc.vnet.net
>
>
> Hi,
>
> Could you explain a mysterious behaviour of "! operator" as shown below?
>
>
> In[43]:=
> MemberQ[{1,2,3},3]
>
> Out[43]=
> True
>
> In[47]:=
> !MemberQ[{1,2,3},3]
> (* Here Mathematica does not give any response! *)
>
> In[48]:=
> Not@MemberQ[{1,2,3},3]
>
> Out[48]=
> False
>
>
> Considering the description from Mathematica help:
> "!expr is the logical NOT function. It gives False if expr is True,
> and True if it is False."
> This behaviour seems quite suspicious?
>
>
> DongGook
>
>
> ----------------------------------
> DongGook Park,
> School of Information Technology,
> SunChon University, Korea
> Telephone: +82 61 750 3597
> Mobile: +82 18 732 2125
> Home page: http://www.dgpark6.com/
> Email: dgpark6 at sunchon.ac.kr
>
>
>
>
>
>
>
>
--
DrBob at bigfoot.com